1. Field of the Invention
The present invention relates to a manual information input device which can be used for inputting information for example into distributed data processing systems.
2. Description of the Background Art
As far as the wide spread of the distributed data processing systems is concerned, the desire nowadays is strong to economically use extended connecting wires between different components of the data processing systems, in particular between input devices and the data processing means.
The large spread of extended multiple wire connecting lines requires great expenditure since such connecting lines use expensive conducting materials, such as copper.
Therefore the problem of reducing costs concerning these connecting wires in order to increase the economy of the distributed data processing systems has become extremely topical.
One attempt to solve this problem is through the reduction of the number of the wires in the connecting lines, in particular through the employment of two-wire connecting lines. However, the employment of such two-wire connecting lines results in a decrease of the operational speed of known input devices and a decrease in their response.
Furthermore, known information input devices have insufficient noise immunity when information is transmitted by long connecting lines and also have a considerable energy consumption.
A conventional input device (Su, A, 1070533) comprises a keyboard consisting of keys, and a sound wave generator is disposed beneath each of the keys. Beneath this, a wave transmitting plate is arranged, which, when contacted by the sound wave generator, transmits ultrasonic waves in all directions from the contact point. This device also comprises sound wave receivers which are arranged such that coordinate values X and Y of a contacting point can be determined within a pre-determined rectangular coordinate system. Thereby the input information can be coded without detecting keys' position. By means of these techniques, the costs of the information input device can be decreased substantially.
However, the device in question requires a coupling of its output with a multiple wire transmitting line, because its output signal is represented by a digital code comprising plural bits. The number of wires of the transmitting line for transmitting such signals is determined by the number of the bits, of which there are usually at least 5.
The experts in this technical field have knowledge that the digital code correspondingly converted which has been generated at the output of said information input device can be serially transmitted through a transmitting line having a reduced number of wires which, however, leads to an substantial decrease in the operational speed of the input device and a prolongation of the information transmission time. I.e., the high operational speed of the above information input device cannot be ascertained without using the multiple wire transmission line.
Further, the reliability of information input by means of the above described device is not high enough due to a complicated signal processing requiring the conversion of the sound signals into electric signals.
Another known information input device (SU, A, 11 15040) has the objective to increase the reliability of the input information. This known input device includes a connecting matrix of conductor lines having a plurality of parallel horizontal row conductor lines and parallel vertical column conductor lines, extending orthogonally to the row conductor lines, and the crossing points of the row conductor lines and the column conductor lines form nodes of the connecting matrix. Further, this known device includes a voltage source for voltage supply, a probe pin being connected to the voltage source and being connectable to the nodes of the connecting matrix for generating signals corresponding to the coordinate information being entered.
These signals are generated time-sequentially by closing the row conductor lines and the column conductor lines crossing in a respective node of the connecting matrix and being energized with an energizing voltage from the voltage source.
Two coded signals comprising five elements are generated sequentially at outputs of an encoding unit being connected to the row conductors of the connecting matrix and to corresponding vertical conductors, said coded signals identifying the input information and representing the signals by pulse amplitude modulation. Therefore, it is required to transmit the parallel codes of said two sequential coded signals by a transmitting line having five wires.
One draw-back of the above described input device according to SU,A,1115040 is that, as in the preceding case, the device cannot guarantee a high operational speed without using a multiple wire transmission line for the transmission of the input information.
It is to be noted that the operational speed of the latter input device is considerably decreased by the fact that for each input of each record the sequential closing of the vertical conductors and the horizontal conductors is required.
Further, as mentioned above, the described device uses pulse amplitude modulation of the signals to be transmitted through each transmission line, wherein the pulse amplitude modulation is known to have a low noise immunity.
By virtue of this low noise immunity, the output signals of the above described input device cannot be transmitted over large distances without being additionally converted, thereby limiting the length of the transmission lines between the information input devices and a data processing apparatus connected thereto.